A randomized placebo-controlled crossover study in healthy male subjects was designed to study the underlying serotonergic alteration in OSA and the 5-HT system in controlling ventilation in humans. Specifically, the study will be divided into two periods: 1)normal brain serotonin period, produced by a carbohydrate-protein balanced diet; and 2)depleted brain serotonin period, produced by a tryptophan-deficient diet. In each period the effects of these diets on ventilatory variability during wakefulness and sleep, upper airway.